FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS (Potential Offset of Counterparty Netting and Cash Collateral) (Details) - Energy Derivative - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Derivative Asset [Abstract]
Derivative Asset, Gross Amount Recognized in the Balance Sheets	$ 6	$ 12
Derivative Asset, Counterparty Netting	4	11
Derivative Asset, Cash Collateral Received/Posted	0	0
Derivative Asset, Net Amount	2	1
Derivative Liability [Abstract]
Derivative Liability, Gross Amount Recognized in the Balance Sheets	(76)	(37)
Derivative Liability, Counterparty Netting	(4)	(11)
Derivative Liability, Cash Collateral Received/Posted	(2)	0
Derivative Liability, Net Amount	$ (70)	$ (26)

Fair value, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, offset against an obligation to return collateral.

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